ABSTRACT The objective of this R21 proposal is to develop and validate a low-cost ?point-of-care? test (POCT) that allows daily monitoring of markers for anticoagulation and thrombosis (?AT-POCT?), to be used by patients with advanced heart failure (AHF) on left ventricular assist device (LVAD) support. This proposal is motivated by 3 reasons: (1) the 2 major complications in this population are bleeding and thrombosis, resulting from the requirement of long-term warfarin anticoagulation to counteract the pro-thrombotic nature of LVAD implants, (2) timely identification and treatment of these complications are critical for avoiding hemodynamic decompensation?particularly in the case of device thrombosis (the most feared complication)?thus warranting more rigorous surveillance than current standard of care, and (3) no POCT currently available allows at-home monitoring of biological indicators of anticoagulation (via INR) and thrombosis (via serum lactate dehydrogenase; LDH) in a reliable and cost-effective manner. To address these concerns, we will develop a low-cost, fully-printed AT-POCT that can simultaneously measure INR and LDH from a drop of fingerstick blood, in format that is handheld, portable, and easy-to-use requiring minimal user intervention. AT-POCT cassettes are fabricated by printing and storing all components required for sample read-out on the assay surface, which is passivated by a non- fouling (protein- and cell-resistant) polymer brush coating that improves performance by eliminating biomolecular noise from nonspecific binding. After 5 minutes of blood incubation, cassettes are read by a handheld, portable detector, whereby serum LDH measurement occurs by optical colorimetry after dissolution and consumption of assay reagents printed into the polymer brush, and INR measurement simultaneously occurs by impedance measurements from printed electronics. Results can be wirelessly transmitted to and reviewed by expert physicians, with abnormal results triggering immediate referral. Robust optical and electrical transduction on this platform have been demonstrated in principle by preliminary studies, ensuring preservation of assay performance even in complex biological milieu (e.g. whole blood). A systematic study assessing a variety of printing conditions and assay formats specifically tailored to INR and LDH measurements will be carried out in parallel, with the goal of down-selecting to final prototypes. Clinically-relevant operation of the AT-POCT will be demonstrated in a small pilot cohort of AHF patients on LVAD support being managed at Duke University Medical Center. This work is potentially transformative because: (1) it will intensify hemodynamic surveillance of LVAD-supported patients, leading to more timely diagnosis of bleeding and thrombotic complications, and hence decrease morbidity and mortality; (2) it offers a scalable and sustainable alternative to traditional in-clinic visits for INR and LDH checks ? this will greatly decrease overall cost, which is critical to help contain soaring healthcare costs associated with the continuously growing AHF demographic; and (3) in the long-term, successful demonstration of this fully-printed and portable POCT will open a new path for low-cost, portable diagnostics operated in a handheld, battery- operated form factor. This platform can be customized to target any analyte for which printable bioassay reagents are available, and is thus broadly applicable to clinical management of other disease states.